Pharmacokinetics of a single inhalation of hydrogen gas in pigs.

Abstract

A porcine experimental model was established to characterize the pharmacokinetics of inhaled hydrogen gas (H2). Catheters were placed in the carotid artery (CA), portal vein (PV), and supra-hepatic inferior vena cava (IVC), and the lungs were filled with 100% H2 to maximum inspiratory capacity, followed by a 30-second breath-hold. Blood samples collected at 0, 3, 10, 30, and 60 minutes were analyzed by gas chromatography. CA H2 concentration peaked immediately after the breath-hold and fell to approximately 1/40 of peak within 3 minutes. Peak concentrations in the PV and IVC reached 40% and 14% of the CA peak, respectively, but their half-lives (310 s and 350 s) were considerably longer than that of the CA (92 s). By 10 minutes, venous H2 exceeded arterial levels. At 60 minutes, portal and superior vena cava blood still contained H2 above baseline, whereas arterial levels had returned to steady state. These findings indicate that inhaled H2 undergoes whole-body distribution via advection-diffusion and is dynamically metabolized.

Mechanism

Inhaled H2 is absorbed across the pulmonary epithelium into the bloodstream and distributed systemically by advection-diffusion. Arterial half-life is approximately 92 seconds, whereas portal and inferior vena cava half-lives exceed 300 seconds, reflecting dynamic hepatic metabolism and slower venous clearance.